The invention relates to a device for the simultaneous application of treatment liquid to both sides of a web, particularly a textile web.
Devices of this general type are disclosed in DE-PS 14 60 265 and DE 37 33 996 C2. In the known embodiments, arranged in the "opposite side surface" of the trough, opposite an inflatable hose, is another such inflatable hose, so that the web passes between the two hoses. The additional hose results in a space requirement corresponding to its cross-section on its side, so that design freedom is limited at this location.
In the device disclosed in DE-PS 14 60 265, the web continues to run vertically downward after passing by the interacting hoses, and passes through a pair of squeezer rollers, in which applied treatment liquid is at least partially squeezed out. In DE 37 33 996 C2, the web also continues vertically downward after passing by the hoses, and is then guided via a deflection roller after a certain distance.
There are treatments of textile webs in which the web demonstrates a strong tendency to shrink after the treatment liquid is applied. This is particularly pronounced when cotton material is saturated with an alkaline solution, as is the case in the mercerization process.
In mercerization, the strong tendency toward shrinkage is counteracted in that, after the mercerization solution is applied, the web is held in a so-called bound web guidance in which the web is guided over a sequence of deflection rollers which rest against one another or virtually rest against one another, and no free web sections whatsoever occur between the deflection rollers. The web is held tightly on the circumference of the deflection rollers, as a result of the friction which comes about from the web tension, in an effort to prevent shrinkage.
A characteristic of the application devices of the type set forth above is the possibility of saturating the web with a relatively high amount of treatment liquid, in the range of 100 to 200% of the mass per unit area. The web is uniformly wiped off at the hoses, and exits the application device with a charge which cannot be easily achieved with other application devices. At the same time, the charge is present on both sides and is actually massaged slightly into the interior of the web when it passes through the slit between the hoses.
It has been shown that if mercerization solution is applied to a textile web with an application device of the type known in the prior art, shrinkage occurs virtually spontaneously. The free web sections which result from DE-PS 14 60 265 and DE 37 33 996 C2 result in unacceptable shrinkage amounts when the application device is used in such a way.